1. Field of the Invention
This invention relates to an exposure control apparatus using an electrically operated optical diaphragm as diaphragm device.
2. Description of the Prior Art
The conventional camera has been using a mechanical diaphragm as its diaphragm device. However, since a mechanical diaphragm device necessitates the use of a complex mechanical mechanism, reduction in size of the camera has been hindered and design latitude has been prevented. Hence there have been proposed various inexpensive, small electrically operated optical diaphragms such as those composed of a Kerr cell, a transparent ferroelectric substance (hereinafter will be called PLZT for short), liquid crystal, an electrochromie element, a Faraday element or an element utilizing electrophoresis. However, with the camera using such an electrically operated optical diaphragm of the prior art, an aperture value thereof remains unchanged once the value is determined. Therefore, when the brightness of an object to be photographed changes, for example, during a shutter release operation or during a cycle of an exposure control operation after determination of an aperture value, such a camera is bound to have an inappropriate exposure value.